nulogy/Gorgon

require 'etc'
require 'fileutils'

module Gorgon
  class ListenerInstaller
    include Configuration

    GORGON_DIR=".gorgon"
    DEFAULT_NO_WORKERS = 4
    LISTENER_CONFIG_FILE = "gorgon_listener.json"
    GORGON_INIT_FILE = "/etc/init/gorgon.conf"

    def self.install
      ListenerInstaller.new.install
    end

    def install
      @configuration = load_configuration_from_file("gorgon.json", merge: "gorgon_secret.json")

      FileUtils.mkdir_p gorgon_dir_path
      Dir.chdir gorgon_dir_path

      create_listener_config_file

      create_gorgon_service

      start_gorgon_daemon
    end

    private

    def gorgon_dir_path
      @gorgon_dir_path ||= "#{Dir.home}/#{GORGON_DIR}"
    end

    def create_listener_config_file
      worker_slots = worker_slots_prompt
      puts "Using #{worker_slots} worker slots"
      amqp_host = @configuration[:connection][:host]
      puts "Amqp host is '#{amqp_host}'"

      puts "Creating #{LISTENER_CONFIG_FILE} in #{Dir.pwd}"
      File.open(LISTENER_CONFIG_FILE, 'w') do |f|
        f.write listener_config(amqp_host, worker_slots)
      end
    end

    def create_gorgon_service
      params = {}
      params[:username] = Etc.getlogin
      params[:rvm_bin_path] = rvm_bin_path
      params[:gemset] = get_current_gemset

      tmp_gorgon_conf = '/tmp/gorgon.conf'
      File.open(tmp_gorgon_conf, 'w') do |f|
        f.write gorgon_conf(params)
      end

      puts "Creating '#{GORGON_INIT_FILE}'"

      system("sudo cp /tmp/gorgon.conf #{GORGON_INIT_FILE}")
    end

    def rvm_bin_path
      cmd = 'which rvm'
      path = get_shell_cmd_output cmd, "Error getting rvm path. Make sure '#{cmd}' works"
      puts "Using '#{path}'"
      path
    end

    def get_current_gemset
      return @gemset unless @gemset.nil?

      cmd = 'rvm current'
      @gemset = get_shell_cmd_output cmd, "Error getting current gem. Make sure '#{cmd}' works"
      puts "Using gemset '#{@gemset}'."
      @gemset
    end

    def get_shell_cmd_output cmd, error_message
      result = `#{cmd}`.strip
      if $?.exitstatus != 0
        $stderr.puts "#{error_message}"
        $stderr.puts "Aborting installation"
        exit
      end
      result
    end

    def start_gorgon_daemon
      system("sudo start gorgon")
    end

    def gem_available?(name)
      Gem::Specification.find_by_name(name)
    rescue Gem::LoadError
      false
    rescue
      Gem.available?(name)
    end

    def worker_slots_prompt
      begin
        puts "Number of worker slots (default #{DEFAULT_NO_WORKERS})?"
        input = $stdin.gets.chomp
        if input == ""
          worker_slots = DEFAULT_NO_WORKERS
          break
        end

        worker_slots = input.to_i
        if worker_slots <= 0 || worker_slots >= 20
          puts "Please, enter a valid number between 0 and 19"
        end
      end while worker_slots <= 0 || worker_slots >= 20
      worker_slots
    end

    def listener_config amqp_host, worker_slots
      <<-CONFIG
{
  "connection": {
    "host": "#{amqp_host}"
  },

  "worker_slots": #{worker_slots},
  "log_file": "/tmp/gorgon-remote.log"
}
      CONFIG
    end

    def gorgon_conf params
      <<-CONF_FILE
description "Start gorgon listener"

start on filesystem or runlevel [2345]
stop on runlevel [!2345]

respawn
respawn limit 10 10

pre-start script

bash << "EOF"
  mkdir -p /var/log/gorgon
  chown -R #{params[:username]} /var/log/gorgon
EOF

end script

exec su - #{params[:username]} -c 'cd #{gorgon_dir_path} && #{params[:rvm_bin_path]} #{params[:gemset]} do gorgon listen >> /var/log/gorgon/gorgon.log 2>&1'
      CONF_FILE
    end
  end
end